Combined tire pressure monitoring and keyless entry receiver

ABSTRACT

A system for monitoring conditions within a tire ( 12 ) including a sensor assembly ( 14 ) including a pressure sensor ( 36 ), an accelerometer ( 34 ), a temperature sensor ( 32 ), and a transmitter ( 40 ) to transmit signals indicative of current tire conditions. A remote transmitter ( 22 ) for actuating a remote keyless entry system ( 19 ) emits a signal to actuate a function of the keyless entry system ( 19 ) such as unlocking doors ( 20 ) of the motor vehicle ( 10 ). A receiver assembly ( 16 ) includes an amplitude shift keyed receiver ( 52 ) and a frequency shift keyed receiver ( 58 ) selectively engagable to receive radio frequency transmissions from the tire monitoring system or the remote keyless entry system ( 19 ).

[0001] The present invention claims priority to U.S. Provisional PatentApplication serial Nos. 60/276,210 filed Mar. 15, 2001; 60/269,959 filedFeb. 20, 2001; 60/276,325 filed Mar. 16, 2001; 60/298,258 Jun. 14, 2001;60/290,923 filed May 15, 2001 and 60/352,489, filed on Jan. 23, 2002.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a system for monitoring conditionswithin a tire, and specifically to a receiver assembly for receivingtransmissions of varying modulations from sensor assemblies within eachof the tires and from a remote keyless entry system. It is becomingincreasingly desirable to continually monitor tire pressures in a motorvehicle during operation. Such constant monitoring of tire pressuresallows an operator to maintain vehicle tire pressures within an optimalrange to optimize fuel economy and handling performance.

[0003] Conventional methods of monitoring tire pressure includepositioning a sensor within each wheel to monitor pressure. The sensorassembly typically emits a radio frequency (RF) transmission indicativeof tire conditions. A receiver disposed within the vehicle receives theRF signal and actuates a messages or warning light to signal theoperator of tire conditions.

[0004] Many motor vehicles include a remote keyless entry systemincluding a key fob carried by an operator to actuate door locks orother features. The remote keyless entry system includes a receiverdisposed within the motor vehicle to receive transmissions from the keyfob and actuate vehicle systems in response to transmissions receivedfrom the key fob. It is known in some system to utilize the same type oftransmission for the tire monitoring system as is used in remote keylessentry system.

[0005] Typically, a transmission is modulated either as an amplitudeshift keyed ASK, or a frequency shift keyed FSK radio frequency. The ASKtransmission modulation is best suited for applications in which thereceiver and transmitter are relative stationary to each other. Inaddition ASK transmissions are favorable when there exists a relativelylong distance between the transmitter and the receiver. However, an ASKtransmission becomes disrupted when the receiver or transmitter ismoving relative to one another. The FSK signal is suited fortransmitters that are moving relative to the receiver because theamplitude remains essentially constant for the duration of anytransmission. However, the FSK transmission has lower peak fieldstrength than a comparable ASK transmission. The FSK transmission isspecifically suited for use with the sensor assembly disposed within thetire and the ASK is suited for use with the remote keyless entry system.

[0006] Accordingly, it is desirable to develop a receiver capable ofreceiving both ASK and FSK transmissions to optimize the capabilities ofboth the tire monitoring system and the remote keyless entry system.

SUMMARY OF THE INVENTION

[0007] An embodiment of this invention is a receiver assembly comprisedof an amplitude key shifted (ASK) receiver and a frequency shift keyed(FSK) receiver for receiving transmissions from sensor assembliesmounted within each of the tires, and from a remote keyless entrysystem.

[0008] A system for monitoring conditions within tires mounted to amotor vehicle includes five tires, each with a sensor assembly. Each ofthe sensor assemblies gathers data indicative of conditions within thetire and transmits that data to a receiver assembly. The receiverassembly in turn forwards that data to a vehicle controller. The vehiclecontroller will then process the data for display to the operator of themotor vehicle.

[0009] Each tire mounts to a rim and each sensor assembly is mountedwithin the rim and includes a valve stem and a circuit housing. Thesensor assembly includes a sensor circuit disposed within the circuithousing. The sensor circuit includes a temperature sensor, a motionsensor and a pressure sensor. An RF transmitter receives data gatheredby the sensors, and relays that data to the receiver.

[0010] Each transmission from the various sensor assemblies includes aunique identity code relating to a specific sensor assembly. Aninitialization or learning mode defines specific sensor assembliesdisposed on a specific motor vehicle. Learning the specific identitycodes of the sensor assemblies eliminates errant reception of othertransmissions from other sensor assemblies installed on other motorvehicles within close proximity.

[0011] The data transmitted from each of the sensor assemblies to thereceiver is transmitted at predetermined intervals. There is aprobability that the receiver will receive two or more datatransmissions from different sensor assemblies at the same time. Thereceipt of two or more data transmission simultaneously or overlapped isknown as a data collision. The receiver will not recognize collided dataor overlapping data transmission, therefore the current inventionprevents overlapping data transmissions by varying the interval betweendata transmission in a random manner. Another factor considered inpreventing signal collision is the transmission rate that affects thelength of time required to transmit data indicative of tire conditions.The faster data is transmitted and received the lower the probability ofdata collision. The shorter the total transmission time, the lower theprobability of signal collision.

[0012] The receiver assembly comprises an amplitude shift key (ASK)receiver and a frequency shift keyed (FSK) receiver. The FSK receiverreceives signals from the sensor assemblies. The ASK receiver receivessignals from a key fob for a remote keyless entry system to initiate thelocking or unlocking of doors.

[0013] The ASK transmissions are favorable for situations where thetransmitter and receiver are substantially stationary. The ASK radiofrequency transmission is easily disrupted by abrupt changes in receivedfield strength and therefore are not favorable for sending transmissionsfrom a moving object such as the tires of a motor vehicle. However, theASK provides for greater signal power which is desirable for the remotekeyless entry system. The FSK transmissions are favorable for conditionswere the transmitter or receiver are moving during data transmission.However, an FSK transmission is amplified upon receipt, effectivelyremoving any amplitude disturbances.

[0014] The receiver assembly switches between the ASK receiver and theFSK receiver in response to a triggering event. The triggering event isthe vehicle speed. At speeds indicative of traveling along a roadway,the FSK receiver is engaged. As appreciated, a motor vehicle travelingat speed along the roadway does not require reception of ASKtransmissions from a remote keyless entry transmitter to unlock thedoors of the motor vehicle. Conversely, a vehicle at rest or parked isunlikely to spontaneously encounter a tire puncture, and therefore atlower speeds the ASK receiver is engaged.

[0015] An intermediate condition is encountered when the motor vehicleis idling. In this condition, the receiver assembly engages the ASKreceiver due to the low speed of the vehicle, however, the tire maybecome punctured or encounter a condition that changes conditions withinthe tire. The signal from the sensor assemblies includes an ASK wake upsignal that proceeds the FSK signal transmitting data indicative ofcurrent conditions within the tire. The ASK wake up signal triggers thechange over from the ASK receiver to the FSK receiver. The FSK receiverremains engaged until the FSK transmission is completed and the ASKreceiver is reengaged.

[0016] The system of this invention includes a receiver capable ofreceiving both ASK and FSK transmissions to optimize the capabilities ofboth the tire monitoring system and the remote keyless entry system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

[0018]FIG. 1 is a schematic view of a motor vehicle including a tiremonitoring and remote keyless entry system;

[0019]FIG. 2 is a cross-sectional view of a tire including a sensorassembly;

[0020]FIG. 3 is a cross-sectional view of the sensor assembly mountedwithin the tire;

[0021]FIG. 4 is a side view of a sensor assembly;

[0022]FIG. 5 is a top view of the sensor assembly;

[0023]FIG. 6 is an exploded view of the sensor assembly;

[0024]FIG. 7 is a schematic view of the circuit assembly within thesensor assembly;

[0025]FIG. 8 is a schematic view of the components of a transmissionfrom the sensor assembly;

[0026]FIG. 9 is a graphical representation of the format of data packetscomprising the transmission from the sensor assembly;

[0027]FIG. 10 is a graph illustrating the effect of transmission rate onsignal overlap in prior art systems;

[0028]FIG. 11 is a graph illustrating how increased transmission rateprevents data overlap;

[0029]FIG. 12 is a schematic view of the receiver assembly;

[0030]FIG. 13 is a schematic view of a motor vehicle and an externaltriggering device to initialize the sensor assemblies;

[0031]FIG. 14 is a schematic view of a method of determining sensorassembly position; and

[0032]FIG. 15 is a schematic view of another embodiment of determiningsensor assembly position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0033] An embodiment of this invention is a system for monitoringconditions within tires mounted to a motor vehicle 10 shownschematically in FIG. 1. The motor vehicle 10 includes four tires 12along with an additional tire 12 carried as a spare. Each of the tires12 includes a sensor assembly 14. Each of the sensor assemblies 14gathers data indicative of conditions within the tire 12 and transmitsthat data to a receiver assembly 16.

[0034] The receiver assembly 16 in turn forwards that data to a vehiclecontroller 18. The vehicle controller 18 will then process the data fordisplay to the operator of the motor vehicle 10 or to the remote keylessentry system 19 to actuate unlocking of doors 20 or other such functionsas are known to a worker skilled in the art. Preferably the remotekeyless entry system 19 is an active system requiring actuation, such asby depressing buttons on the key fob 22, however, it is within thecontemplation of this invention for passive remote keyless entry systemthat do not require a positive action by the operator.

[0035] Referring to FIGS. 2 and 3, each tire 12 mounts to a rim 24. Eachsensor assembly 14 is mounted within the rim 24 and includes a valvestem 26 and a circuit housing 28. The circuit housing 28 is preferablymounted within the tire 12 and the valve stem 26 extends from thecircuit housing 28 outward to provide a means of filling the tire 12with air. A sensor circuit 46 disposed within the circuit housing 28preferably includes a pressure sensor 36, a temperature sensor 32 and anaccelerometer 34.

[0036] Referring to FIGS. 4-6, the valve stem 26 is pivotally mounted tothe circuit housing 28 to provide for use in rims 24 of variousconfigurations. The valve stem 26 is pivotally mounted to the circuithousing 28 and locked in a desired pivotal location by a lock nut 30.Pivotal adjustment of the valve stem 26 relative to the circuit housing28 allows for use of the sensor assembly 14 with various configurationsof wheel rims 24 (FIGS. 3 and 4).

[0037]FIG. 7, is a schematic view of the sensor circuit 46 disposedwithin the circuit housing 28. The sensor circuit 46 includes thetemperature sensor 32, the accelerometer 34 and the pressure sensor 36.Each of the sensors 32, 34 and 36 are of any configuration known to aworker skilled in the art. An RF transmitter 40 receives data gatheredby the sensors 32, 34, and 36 and transmits that data to the receiver16.

[0038] A battery 38 powers the sensor circuit 46. A battery monitor 40measure battery 38 power and provides a warning indicator that is sentto the receiver assembly 16 when remaining battery power attains adesired level. The receiver assembly 16 forwards the low battery signalto the vehicle controller 18 and in turn to the operator. Preferably thelife of the battery 38 is of an extended length such that any necessarybattery change is infrequent throughout the life span of the motorvehicle 10. A controller 42 controls how the RF transmitter 42 emitsdata indicative of tire conditions.

[0039] The sensor circuit 46 also includes a low frequency receiver 42.The low frequency receiver 42 receives signals generated to initiate thetransmission of an identity code 68 (FIG. 8) from the sensor assembly 14in order to initialize and localize the sensor assembly 14.Initialization of the sensor assembly 14 teaches the receiver assembly16 the identity codes of each sensor assembly 14 installed on the motorvehicle 10 so that the receiver assembly 16 can ignore transmissionreceived from sensor assemblies 14 of other motor vehicles. Localizationteaches the receiver 16 and controller 18 the specific tire position ofthe sensor assembly 14 on the particular vehicle. The tire positionincludes left front tire, right front tire, left rear tire, and rightrear tire.

[0040] Referring to FIG. 8, a transmission 64 emitted by the sensorassembly 14 includes an ASK wakeup signal 66, an identity code 68 and adata signal 70. The transmission 64 is a FSK transmission, except forthe ASK wake up signal 66.

[0041] Referring to FIG. 9, each data transmission 64 includes a numberof data frames 72. Preferably, three (3) data frames 72 are sent foreach transmission 64. The data transmitted from the sensor assemblies 14to the receiver assembly 16 are transmitted at predetermined intervals80. There is a probability that transmissions from the various sensorassemblies 14 to the receiver assembly 16 will arrive at the same time(schematically indicated at 78). The receipt of two or more data frames72 simultaneously or overlapped, as shown at 78, is known as a datacollision. The receiver assembly 16 will not recognize collided oroverlapping data transmission because the overlapped data frames 78 areof a greater duration than the receiver assembly 16 is programmed toreceive. Overlapping data frames 72 cause the receiver assembly 16 toignore the data frames 78. Repeated data collisions would eliminate datatransmitted from at least two of the sensor assemblies 14.

[0042] The system of this invention includes a method of preventingrepeated data collisions. The sensor assemblies 14 of this inventionprevent overlapping data frames 72 by varying the predetermined interval80 between data frames 72 in a random manner. The length of the dataframe 72 is preferably 50 milli-seconds (ms) with the interval 80varying according to the below listed equation.

Interval length=standard length * (beta * standard length)

[0043] Where:

[0044] interval length is the length of time in ms between data frames;

[0045] Standard length is a predetermined duration of time in ms; and

[0046] Beta is a random variable with a value between 0 and 1.

[0047] Preferably the standard length of time is 100 ms; therefore theinterval length will vary between 100 ms and 200 ms depending on thevalue of beta. Each transmission from the sensor assemblies 14 are sentwith differing variable intervals 80, such that even if one or more datapackets 72 overlap for any one transmission, subsequent data packets 72will not overlap, thereby preventing cyclical, or repeated overlap. Asappreciated, differing intervals and lengths of data frames are withinthe contemplation of this invention, and a worker skilled in the artwould recognize the application of this method to other lengths of datatransmission.

[0048] In another embodiment of this invention, the length of thevariable interval 80 is transmitted to the receiver assembly 16. Thereceiver assembly 12 will then expect the next data packet 72 at thecommunicated interval. This allows the receiver assembly 16 to switchback to the ASK receiver between data frames 72.

[0049] Another factor considered in preventing signal collision is thetransmission rate. The faster data is transmitted and received the lowerthe probability of data collision. Prior art FIG. 10 illustrates thelikelihood of signal collisions at a transmission rate of 4 kbaud. Eachline represents the length of time required to transmit each data frame72 from each of the sensor assemblies 14. FIG. 11 illustrates how theincrease in baud rate decreases the probability of overlapping dataframes 72. Each line represents a length of time to transmit one dataframe 72 to the receiver assembly 16. The shorter the total transmissiontime, the lower the probability of signal collision. Preferably, thesystem of this invention includes a baud rate of 10 kbaud as shown inFIG. 11, however, a worker skilled in the art would understand thatdifferent data transmission rates are within the contemplation of thisinvention.

[0050] Referring to FIGS. 1 and 12 the receiver assembly 16 comprises anASK receiver 52 and a FSK receiver 58. The FSK receiver 58 receivessignals from the sensor assemblies 14. The ASK receiver receives signalsfrom a key fob 22 for the remote keyless entry system 19 to initiate theunlocking of doors 20. The receiver assembly 16 also includes an antenna48 to receive transmissions from the key fob 22 and the sensorassemblies 14. The receiver assembly 16 includes a low frequency driver50 to emit a signal to the sensor assemblies 14 to initiate transmissionby the sensor assemblies 14.

[0051] The antenna 48 is preferably of a length one quarter that of thewavelength of the transmission received. Transmissions received by theantenna 48 proceed through a resistor 54 to the RF receiver 16. Acontroller 60 controls which of the receivers 58 and 52 are engaged toreceive incoming transmissions.

[0052] Transmission from the various sensor assemblies 14 include theunique identity code 68 (FIG. 8) relating to a specific sensor assembly14. The initialization or learning mode defines the specific sensorassemblies 14 disposed on a specific motor vehicle. Learning thespecific identity codes 68 of each of the sensor assemblies 14eliminates errant reception of other transmissions from other sensorassemblies 14 installed on other motor vehicles. Initialization occursby matching the sensor assemblies 14 of a specific motor vehicle withthe receiver assembly 16 of that motor vehicle. The receiver assembly 16disposed within the motor vehicle 10 will receive numerous signals fromsurrounding RF transmitting sources such as radios, electricalappliances and other vehicle systems equipped with similar tire sensingsystems.

[0053] Referring to FIG. 13, an embodiment of initialization includesplacing the receiver assembly 16 (FIG. 1) in a learn mode and actuatingeach sensor assembly 14 through the use of a triggering device,schematically shown at 84. The triggering device can be a magnet, atransponder located at a programming station or a low frequency emitterpositioned on the motor vehicle. The triggering device 84 initiates eachsensor assembly 14 in sequence to transmit the identity code 68. Thesequence of initiating transmission of the identity code 68 indicatesthe location of the sensor assembly 14 on the motor vehicle 10. Thefirst sensor assembly 14 triggered is the front left tire, the second isthe front right and so on until all the tires on the motor vehicle havebeen triggered to transmit the identity code 68 to the receiver assembly16. The identity code 68 is stored sequentially to indicate the positionof the specific sensor assembly 14. The receiver assembly 16 learnswhich sensor assembly 14 belongs to the specific motor vehicle. Inaddition to the specific location on the sensor assembly on the motorvehicle such as the front right or front left tire is also recorded inthe receiver assembly 16. This operation is repeated any time the tires12 of the motor vehicle are changed or rotated.

[0054] Another embodiment of initialization requires no externaltrigger. Instead an acceleration value from the motor vehicle 10 iscommunicated to the vehicle controller 18 and compared to accelerometerdata transmitted from each of the sensor assemblies 14. Theaccelerometer 34 of each sensor assembly 14 transmits accelerationinformation of the tire 12. The acceleration value of each tire 12 iscompared to the acceleration value provided by another vehicle system,such as the anti-lock braking system or transmission system (indicatedschematically in FIG. 1 at 86). If the acceleration signals are equalwithin a predetermined tolerance value, the identity code 68 sent withinthe transmission from the sensor assembly 14 will be recorded asbelonging to the specific motor vehicle.

[0055] The initialization or learning process using the compared valuesof acceleration may be repeated whenever the motor vehicle 10 is in anon-moving position for a predetermined length of time. The purpose ofthe relearning of the sensor assembly identification codes is to allowfor changing or rotating of the tires 12 and thereby the sensor assembly14. The predetermined amount of time allows for the possibility that oneof the sensor assemblies 14 may have been changed, for instance when aspare tire is installed.

[0056] In the instance, where a new tire, and thereby a new sensorassembly 14 is installed, the receiver assembly 16 receives the newidentity code of the new sensor assembly 14 during initial movement ofthe motor vehicle 10. The receiver assembly 16 compares the accelerationsignal belonging to the new identity code of the new sensor 14 andcompares it to the acceleration of the vehicle 10. If the vehicleacceleration is comparable, the receiver assembly 16 will recognize thenew sensor assembly 14 after a predetermined amount of time or number ofdata frames. This is transparent to the operator of the motor vehicle.

[0057] Referring to FIG. 14, in another embodiment of this invention,localization of each of the sensor assemblies 14 is established bycomparing data obtained from another vehicle system 86 indicative of aturn of the motor vehicle 10. The tires 12 of a motor vehicle traveldifferent distances when turning. The inner tires 88 travel along afirst radius indicated at r1 and the outer tires 90 move along a secondradius r2. Acceleration and turning data is compared to the accelerationat each wheel. Data transmitted from a sensor assembly 14 mounted to oneof the inner tires 88 of the motor vehicle will indicate a loweracceleration than that of a sensor assembly 14 mounted to on of theoutside wheels 90. Therefore, the side that the sensor assembly 14 ispositioned is indicated by the magnitude of acceleration of that tirerelative to the acceleration and direction of the motor vehicle 10.Accelerometer correlation determines whether the sensor assembly is onthe left or right side of the motor vehicle 10, however, this does notindicate whether the sensor assembly 14 is a front or rear tire.

[0058] In one embodiment of localization the front to rear location ofthe tire 12 is accomplished by detecting signal strength of thetransmission sent from each of the sensor assemblies 14. In thisembodiment, the receiver assembly 16 includes front and rear antennas92, 94. Transmissions received at each antenna 92,94 are measured forfield strength. The rear antenna 94 will receive transmissions havinghigher field strength from the sensor assemblies 14 disposed on the reartires of the motor vehicle 10. The front antenna 92 will receive astronger transmission from sensor assemblies 14 disposed on the fronttires of the motor vehicle 10. The field strength data provides the dataindicating the front or rear position of each sensor assembly 14 and theacceleration data correlated to the turning radius of the motor vehicle10 provides the left or right position of each of the sensor assemblies14.

[0059] Referring to FIG. 15, another embodiment of localization combineslow frequency transmissions with correlation of acceleration todetermine the position of the sensor assemblies 14. Low frequencyemitters 96 are positioned to initiate transmission from the rear sensorassemblies 14. A transmission from the low frequency emitter triggersthe transmission of the rear sensor assemblies 14 that is then receivedby the receiver assembly 16 to indicate a rear location of the tires 12.This provides the data required to determine the front and rear positionof any particular sensor assembly 14. The left and right position isdetermined by correlating accelerometer data obtained from each of thesensor assemblies 14. Further, a worker knowledgeable in the art willrecognize that other combination of low frequency initiatingtransmissions and correlation of accelerometer data can be used todetermine the specific location of any of the sensor assemblies 14disposed on the motor vehicle 10.

[0060] The receiver assembly 16 of this system is also used with theremote keyless entry system 19. The receiver assembly 16 is configuredto receive transmission from both the sensor assemblies 14 and the keyfob 22 (FIG. 1). Although a key fob 22 is specifically described it iswithin the contemplation of this invention that the remote entry system19 include other active or passive transmitting means to initiate entryor operation of the motor vehicle 10.

[0061] The receiver assembly 16 includes the ASK receiver 52 and the FSKreceiver 58. This configuration allows the receiver assembly 16 to beused for both the remote keyless entry system 19 and the tire monitoringsystem.

[0062] ASK transmissions are favorable for situations where thetransmitter and receiver are substantially stationary. The ASK radiofrequency transmission is easily disrupted by abrupt changes in receivedfield strength and therefore are not favorable sending transmission froma moving object such as the tires 12 of a motor vehicle 10. The changesfrom received field strength can change for any number or reasons withina motor vehicle including interference created by other onboard systems,to the specific environment present at the time of the signal. However,the ASK provides for greater signal power which is desirable for theremote keyless entry system of this invention. The ASK transmissionallows for higher peak output field strength, relative to a comparableFSK transmission. However, the ASK transmission decreases typicalbattery life and is therefore not desirable for applications such astire condition sensing that require longer battery life due to thedifficulty of changing batteries of the sensor assemblies disposedwithin the tire of the motor vehicle.

[0063] FSK transmissions are favorable for conditions were thetransmitter or receiver are moving during data transmission. Asappreciated, rotation of a tire will introduce amplitude variations inthe transmission caused by the changes in interference patterns. Ifsensor assembly 14 data was transmitted by way of an ASK transmission,the noise caused by rotation of the tire would cause data in thetransmission to become corrupted. However, an FSK transmission isamplified upon receipt to effectively remove any amplitude disturbances.Further, the FSK transmission is less power intensive and therefore moreadaptable to the sensor assembly application that requires longerbattery life.

[0064] Referring to FIG. 12, the receiver assembly 16 defaults tosending any transmission to the ASK receiver 52. The ASK receiver 52operates at a lower power and is therefore the default receiver that ison when the receiver assembly 16 is activated. The ASK receiver 52 isengaged while the motor vehicle 10 is stopped or parked. Preferably, theASK receiver 52 is engaged in response to the speed of the motor vehiclebeing below a predetermined speed. Preferably, the predetermined speedis 10 mph. Above 10 mph, the receiver assembly 16 will change over tothe FSK receiver 58. The switch is initiated because it is unlikely thatthe remote keyless entry system 19 will be activated while the vehicle10 is traveling at speed. The FSK receiver 58 will then receivetransmissions from the sensor assemblies 14.

[0065] The conditions of the motor vehicle 10 traveling above thedesired speed or in a parked position provide definite indicators forthe switch between FSK and ASK receivers 58, 52. However, when thevehicle 10 is idling, for instance in a traffic jam, but not moving atthe desired speed to switch from the ASK receiver 52 and the FSKreceiver 58 the system will not switch over to the FSK receiver 58unless another conditions is satisfied. Each transmission 64 (FIG. 8)includes the ASK wake up signal 66 that is sent prior to the FSKtransmission. The ASK wake up signal 66 alerts the receiver assembly 16to incoming FSK transmission, which causes the receiver assembly 16 toswitch over to the FSK receiver 58. The switch over allows the receiverassembly 16 to accept data indicative of tire conditions from the sensorassemblies 14 while the automobile is parked or idling in traffic.

[0066] Preferably, each of the sensor assemblies 14 will transmit asignal indicative of tire conditions at differing rates depending on thespeed of the motor vehicle. At speeds above a predetermined speed thesensor assemblies 14 will transmit tire condition data at a greaterfrequency. At lower speeds, indicative of a parked vehicle, the sensorassemblies 14 transmit at a lower rate. Preferably, the predeterminedspeed is 10 mph and the sensor assemblies 14 will transmit signalsindicative of tire conditions once every minute. Below the 10 mphpredetermined speed threshold the sensor assemblies 14 will transmitsignals only after sensing a change in tire pressure above a desiredamount indicative of a tire 12 losing air pressure. Once an initial lossof pressure is sensed, the sensor assemblies 14 are triggered totransmit signals at one-minute intervals. Although, specific speeds andintervals of data transmission are discussed, a worker knowledgeable inthe art will understand that it is within the contemplation of thisinvention to use other speeds and data transmission intervals accordingto specific application criteria. The selective actuation of thetransmitter 40 for each sensor assembly and the switching between theASK and FSK receivers 52,58 prevent signal collisions between ASK andFSK transmission emitted by the remote keyless entry system 19 and thetire monitoring system. Preventing signal collisions optimizes functionof the receiver assembly 16.

[0067] The foregoing description is exemplary and not just a materialspecification. The invention has been described in an illustrativemanner, and should be understood that the terminology used is intendedto be in the nature of words of description rather than of limitation.Many modifications and variations of the present invention are possiblein light of the above teachings. The preferred embodiments of thisinvention have been disclosed, however, one of ordinary skill in the artwould recognize that certain modifications are within the scope of thisinvention. It is understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed. For that reason the following claims should be studied todetermine the true scope and content of this invention.

What is claimed is:
 1. A system for monitoring conditions within a tirecomprising; a sensor assembly disposed within each tire of a motorvehicle, a transmitter in communication with said sensor assembly totransmit signals indicative of current tire conditions; a remotetransmitter for actuating a remote keyless entry system, said remotetransmitter emitting a signal to actuate a function of said keylessentry system; a receiver assembly for receiving said signal indicativeof said current tire conditions and said single to actuate a functionfrom said remote transmitter, said signal indicative of said tireconditions is different than said signal to actuate a function of saidremote keyless entry system.
 2. The system of claim 1, wherein saidsignal indicative of said current tire conditions is a frequency shiftkeyed transmission.
 3. The system of claim 1, wherein said signal toactuate a function of said remote keyless entry system is an amplitudeshift keyed transmission.
 4. The system of claim 1, wherein saidreceiver assembly includes an amplitude shift keyed receiver, and afrequency shift keyed receiver, said receivers selectively engaged toreceive incoming signals in response to a predetermined triggeringevent.
 5. The system of claim 4, wherein said predetermined triggeringevent is the current speed of the motor vehicle.
 6. The system of claim5, wherein said amplitude shift keyed receiver is engaged to receiveincoming signals for speeds below a predetermined speed threshold ofsaid motor vehicle and said frequency shift keyed receiver is engaged toreceive incoming signals for speeds above said predetermined speedthreshold.
 7. The system of claim 5, wherein said signal indicative ofsaid tire conditions includes an amplitude shift keyed wake up signal,said amplitude shift keyed wake up single initiating a switch from saidamplitude shift keyed receiver to said frequency shift keyed receiver.8. The system of claim 1, wherein said transmitter sends said signal atpredetermined intervals, said predetermined intervals varied in responseto motor vehicle speed.
 9. The system of claim 1, wherein saidpredetermined interval is greater at speeds above said predeterminedspeed threshold than below said predetermined speed threshold.
 10. Thesystem of claim 9, wherein said predetermined interval increases inresponse to variation of pressure within one of said tires.
 11. Thesystem of claim 1, wherein said signal indicative of said tireconditions includes a plurality of data frames sent at random timeintervals to prevent repeated overlap of transmissions from two or moreof said sensor assemblies.
 12. The system of claim 11, wherein saidrandom time interval is transmitted to said receiver assembly such thatsaid receiver assembly anticipates subsequent data frames of saidsignal.
 13. The system of claim 12, wherein said amplitude shift keyedreceiver is engaged during said random time interval.
 14. The system ofclaim 1, wherein said sensor assembly includes a valve stem pivotallymounted to said sensor assembly and lockable at a desired pivotedposition.
 15. The system of claim 1, wherein said sensor assemblyincludes a temperature sensor.
 16. The system of claim 1, wherein saidsensor assembly includes an accelerometer.
 17. The system of claim 1,wherein said receiver assembly includes a learning mode for discerningbetween signals from sensor assemblies disposed on other motor vehicles;said learning mode compares an acceleration value obtained from saidsensor assembly with a vehicle acceleration value to distinguish betweensensor assemblies disposed on another motor vehicle.
 18. The system ofclaim 1, where said receiver assembly includes a localization mode fordiscerning the specific position of the tire on the motor vehicle, saidlocalization mode includes an external triggering source to initiatespecific transmission from a specific sensor assembly associated with aspecific location on said motor vehicle.
 19. A receiver assembly forreceiving signals indicative of tire conditions for a tire pressuremonitoring system and signals initiating activation of a specificfunction for a remote keyless entry system comprising; an amplitudeshift keyed receiver; a frequency shift keyed receiver; said receiversselectively engaged to receive incoming signals in response to atriggering event.
 20. The assembly of claim 19, wherein said triggeringevent is a predetermined speed of the motor vehicle.
 21. The assembly ofclaim 19, wherein said tire pressure monitoring system includes a sensorassembly, said sensor assembly including a transmitter emitting thesignal indicative of tire conditions, said signal is a frequency shiftkeyed transmission.
 22. The assembly of claim 19, wherein said remotekeyless entry system includes a remote transmitter, said remotetransmitter emitting an amplitude shift keyed transmission.
 23. Thesystem of claim 19, wherein said amplitude shift keyed receiver isengaged to receive incoming signals for speeds below a predeterminedspeed threshold of said motor vehicle and said frequency shift keyedreceiver is engaged to receive incoming signals for speeds above saidpredetermined speed threshold.
 24. The system of claim 23, wherein saidtire monitoring system emits a single indicative of tire conditions andincludes an amplitude shift keyed wake up single, said amplitude shiftkeyed wake up signal initiating a switch from said amplitude shift keyedreceiver to said frequency shift keyed receiver.
 25. A method ofdetermining a position of sensor assemblies for a tire pressuremonitoring system of a motor vehicle comprising the steps of: a.transmitting a signal indicative of tire acceleration to a receiverassembly; b. obtaining data indicative of motor vehicle speed from avehicle system; c. comparing the signal indicative of tire accelerationwith the data indicative of motor vehicle acceleration; d. recording thesensor assembly identification code in response to the signal indicativeof tire acceleration being substantially equal to the data indicative ofmotor vehicle acceleration.
 26. The method of claim 25, furtherincluding the step of relearning sensor assembly position in response tothe motor vehicle remaining stationary for a predetermined period oftime.
 27. The method of claim 25, further including the step ofrecognizing a new sensor assembly in response to receiving a desirednumber of data indicative of tire acceleration that compare favorablywith the acceleration data indicative of the speed of the motor vehicle.28. The method of claim 25, further including the step of obtaining dataindicative of a turn of the motor vehicle from a vehicle system, andcorrelating the data indicative of a turn of the motor vehicle toindicate the position of the sensor assembly on the motor vehicle. 29.The method of claim 25, further including the step of measuring signalstrength to determine the position of said sensor assembly.
 30. A methodof preventing data transmission overlap between signals emitted from atire pressure monitoring system and a remote keyless entry system, saidmethod comprising the steps of; a. setting a receiver assembly includingan amplitude shift keyed receiver and a frequency shift keyed receiversuch that incoming transmissions are received by said amplitude shiftkeyed receiver; b. switching from said amplitude shift keyed receiver tosaid frequency shift receiver in response to a triggering event.
 31. Themethod of claim 30, further including the steps of emitting a frequencyshift keyed transmission from said tire pressure monitoring system, andemitting an amplitude shift keyed transmission from said remote keylessentry system.
 32. The method of claim 30, wherein said triggering eventis further defined as obtaining a vehicle speed above a predeterminedthreshold value.
 33. The method of claim 30, wherein said trigger eventis further defined as receiving an amplitude shift keyed wake up signalfrom the tire pressure monitoring system alerting the receiver assemblyto a subsequent frequency shift keyed transmission.